when you say RTS, people immediately think about strategy games such as warcraft ladder, starcraft, age of empires etc. and usually involves building units and killing other units.
now i don't know why ur asking for the definition, but i assumed that you want to explain to some other kids what type of game you're playing. if this is the case, i wouldn't go out and say that sheeptag is a RTS. i'd just explain how sheeptag works and try to make them understand the basics of basically hunting and surviving through strategy, skill and teamwork.